Late Mesoproterozoic low-P/T−type metamorphism in the North Wulan terrane: Implications for the assembly of Rodinia

2021 ◽  
Author(s):  
Lu Wang ◽  
Stephen T. Johnston ◽  
Nengsong Chen ◽  
Heng Wang ◽  
Bin Xia ◽  
...  
Keyword(s):  
Regional Metamorphism ◽  
Age Groups ◽  
Granulite Facies ◽  
Oceanic Lithosphere ◽  
Granulite Facies Metamorphism ◽  
The North ◽  
Tarim Block ◽  
History Of ◽  
Peak Metamorphism ◽  
T Path

Regional metamorphism provides critical constraints for unravelling lithosphere evolution and geodynamic settings, especially in an orogenic system. Recently, there has been a debate on the Rodinia-forming Tarimian orogeny within the Greater Tarim block in NW China. The North Wulan terrane, involved in the Paleozoic Qilian orogen, was once part of the Greater Tarim block. This investigation of petrography, whole-rock and mineral geochemistry, phase equilibrium modeling, and in situ monazite U-Pb dating of garnetite, pelitic gneiss, and quartz schist samples from the Statherian−Calymmian unit of the North Wulan terrane provides new constraints on the evolutionary history of the Greater Tarim block at the end of the Mesoproterozoic during the assembly of Rodinia. The studied samples yielded three monazite U-Pb age groups of ca. 1.32 Ga, 1.1 Ga, and 0.45 Ga that are interpreted to be metamorphic in origin. The tectonic significance of the early ca. 1.32 Ga metamorphism is uncertain and may indicate an extensional setting associated with the final breakup of Columbia. The ca. 1.1 Ga low-pressure, high-temperature (low-P/T)−type granulite-facies metamorphism is well preserved and characterized by a clockwise P-T path with a minimum estimation of ∼840−900 °C and ∼7−11 kbar for peak metamorphism, followed by postpeak decompression and cooling. A tectonothermal disturbance occurred at ca. 0.45 Ga, but with limited influence on the preexisting mineral compositions of the studied samples. The characteristics of the metamorphism indicate an arc−back-arc environment with ongoing subduction of oceanic lithosphere at ca. 1.1 Ga. Combined with previous studies, we suggest that the Greater Tarim block probably experienced a prolonged subduction-to-collision process at ca. 1.1−0.9 Ga during the assembly of Rodinia, with a position between western Laurentia and India−East Antarctica.

Mineralogy and metamorphic history of norite dykes within granulite facies gneisses from Sand Mata, Rajasthan, NW India

1987 ◽  
Vol 51 (360) ◽  
pp. 207-215 ◽  
Author(s):  
Ram S. Sharma ◽  
Jane D. Sills ◽  
M. Joshi
Keyword(s):  
Country Rock ◽  
Granulite Facies ◽  
Slow Cooling ◽  
Granulite Facies Metamorphism ◽  
Tholeiitic Magma ◽  
Metamorphic History ◽  
Gneiss Complex ◽  
Corona Formation ◽  
History Of ◽  
Mineral Compositions

AbstractMetanorite dykes intrude the Banded Gneiss Complex at various places in Rajasthan, N.W. India. They show neither chilled margins nor gradational contacts with the country rock amphibolite or granulite facies gneisses. They have ophitic to subophitic texture with strongly zoned subcalcic clinopyroxene and orthopyroxene, olivine and plagioclase, with subsidiary biotite. During slow cooling a series of reaction coronas developed with garnet forming round biotite, ilmenite and orthopyroxene; hornblende round pyroxenes and orthopyroxene, hornblende ± spinel round olivine, which may be totally replaced. It is inferred that the dykes crystallised from a tholeiitic magma at about 1100-1150 °C and were intruded during the waning stages of granulite facies metamorphism. The corona minerals grew at about 650–700 °C. A series of reactions to account for the development of the coronas is proposed using measured mineral compositions. Although these reactions do not balance for individual corona formation, metamorphism was probably isochemical with Ca, Na, K, Ti, Si and H2O only mobile on the scale of a thin section. Si and H2O were possibly mobile on a larger scale.

Biological aspects of juvenile great hammerhead sharks Sphyrna mokarran from the Arabian Gulf

2021 ◽  
Vol 72 (1) ◽  
pp. 110
Author(s):  
Hua Hsun Hsu ◽  
Zahid Muhammed Nazeer ◽  
Yu Jia Lin ◽  
Premlal Panickan ◽  
Khaled Al-Abdulkader ◽  
...  
Keyword(s):  
Life History ◽  
Arabian Gulf ◽  
Age Groups ◽  
Western Indian Ocean ◽  
Growth Function ◽  
The North ◽  
Von Bertalanffy Growth Function ◽  
Growth History ◽  
History Of ◽  
Hammerhead Sharks

The life history of the critically endangered great hammerhead Sphyrna mokarran was examined using samples collected from commercial fisheries operating in Saudi Arabian waters of the Arabian Gulf. In all, 105 specimens (47 males, 58 females), with a total length (TL) ranging from 67.0 to 236.0cm, were examined between April 2016 and November 2019. All individuals were immature. A neonate measuring 67.0cm TL caught in early June suggested the parturition period of this species was during May and June. Vertebrae under the first dorsal fin from 69 individuals (30 males, 39 females) were processed. Three age groups, from 0+ to 2+ years old, were identified by vertebrae analysis. Based on the relationship between vertebral central diameter and TL, the Fraser–Lee approach was used to back-calculate the growth history of TL. A two-parameter von Bertalanffy growth function provided the best fit to describe early growth of great hammerheads during 0–2.9 years of age based on observed and back-calculated length-at-age data. The asymptotic lengths and k values were estimated to be 256.8cm TL and 0.449 year–1 respectively. This study provides the first life history information of great hammerhead sharks in the north-western Indian Ocean.

Late Paleoproterozoic granulite-facies metamorphism in the North Altyn Tagh area, southeastern Tarim craton: Pressure-temperature paths, zircon U-Pb ages, and tectonic implications

2019 ◽  
Vol 131 (9-10) ◽  
pp. 1591-1606 ◽  
Author(s):  
Hailin Wu ◽  
Wenbin Zhu ◽  
Rongfeng Ge
Keyword(s):  
Granulite Facies ◽  
Mineral Chemistry ◽  
Crustal Thickening ◽  
Granulite Facies Metamorphism ◽  
Magmatic Arc ◽  
Collisional Orogen ◽  
The North ◽  
Altyn Tagh ◽  
Facies Metamorphism ◽  
Tarim Craton

Abstract Granulite occupies the root of orogenic belts, and understanding its formation and evolution may provide critical information on orogenic processes. Previous studies have mainly focused on garnet-bearing high-pressure and medium-pressure granulites, whereas the metamorphic evolution and pressure-temperature (P-T) paths of garnet-absent, low-pressure granulites are more difficult to constrain. Here, we present zircon U-Pb ages and mineral chemistry for a suite of newly discovered two-pyroxene granulites in the North Altyn Tagh area, southeastern Tarim craton, northwestern China. Conventional geothermobarometry and phase equilibrium modeling revealed that these rocks experienced a peak granulite-facies metamorphism at T = 790–890 °C and P = 8–11 kbar. The mineral compositions and retrograde symplectites record a clockwise cooling and exhumation path, possibly involving near-isothermal decompression followed by near-isobaric cooling. Zircon U-Pb dating yielded a ca. 1.97 Ga metamorphic age, which likely represents the initial cooling age, based on Ti-in-zircon thermometry. Combined with regional geological records, we interpret that these granulites originated from the basement rocks of a late Paleoproterozoic magmatic arc that was subsequently involved in a collisional orogen in the southern Tarim craton, presumably related to the assembly of the Columbia/Nuna supercontinent. The clockwise P-T paths of the granulites record crustal thickening and burial followed by crustal thinning and exhumation in the upper plate of the collisional orogen. Our data indicate that the initial exhumation of this orogen probably occurred no later than ca. 1.97 Ga, which is supported by widespread 1.93–1.85 Ga postorogenic magmatism in this area.

Metamorphic evolution and zircon geochronology of early Proterozoic granulites in the Aravalli Mountains of northwestern India

2005 ◽  
Vol 142 (3) ◽  
pp. 287-302 ◽  
Author(s):  
A. B. ROY ◽  
ALFRED KRÖNER ◽  
P. K. BHATTACHAYA ◽  
SANJEEV RATHORE
Keyword(s):  
Granite Gneiss ◽  
Granulite Facies ◽  
Granulite Facies Metamorphism ◽  
Granulite Metamorphism ◽  
History Of ◽  
Single Zircon ◽  
Northwest India ◽  
Orogenic Cycle ◽  
Age Range ◽  
Rock Association

Granulites including a charnockite suite, mafic granulites, pelitic granulites, metanorite dykes and their retrograde varieties occur as discontinuous shear zone-bounded bodies within the Archaean basement comprising a granite gneiss–amphibolite–metasedimentary rock association in the central part of the Aravalli Mountains, northwest India. The entire suite, named the Sandmata Complex, preserves a complex history of tectonothermal evolution. Except for their strongly foliated margins, the granulite bodies are largely massive. Partial melting in the ‘country rocks’ led to the development of migmatite gneisses close to the contact of the granulite, a feature not as common in the rocks further away from the granulite contact. Geothermobarometry of massive granulites indicates Tmax>900°C and Pmax∼7.5 kbar. The retrograde granulites, which formed at lower amphibolite/upper greenschist-facies conditions, experienced channelized hydration reactions concomitant with shearing. These rocks locally appear as hornblende–biotite-bearing foliated granulite with or without Cpx or Opx. The rocks seem to have followed an inverse PTt path and have undergone an earlier phase of near-isobaric cooling. Our single zircon Pb–Pb ages indicate that the exhumation of granulites to the shallower amphibolite-facies levels with concomitant melting in the country rocks took place between 1690 Ma and 1621 Ma. Assuming that the granulite-facies metamorphism took place at around 1725 Ma, we relate the entire process of granulite metamorphism and exhumation covering an age range between 1725 and 1621 Ma to the rift basin opening stages of the Delhi Orogenic cycle that culminated at c. 1450 Ma.

Stable coexistence of grandidierite and kornerupine during medium pressure granulite facies metamorphism

1995 ◽  
Vol 59 (395) ◽  
pp. 327-339 ◽  
Author(s):  
C. J. Carson ◽  
M. Hand ◽  
P. H. G. M. Dirks
Keyword(s):  
Granulite Facies ◽  
Crustal Thickening ◽  
Coarse Grained ◽  
Granulite Facies Metamorphism ◽  
Larsemann Hills ◽  
Facies Metamorphism ◽  
Peak Metamorphism ◽  
Isothermal Decompression ◽  
The Stability ◽  
New Occurrences

AbstractPetrological and mineral chemical data are presented for two new occurrences of co-existing borosilicate minerals in the Larsemann Hills, East Antarctica. The assemblages contain kornerupine and the rare borosilicate, grandidierite (Mg,Fe)A13BSiO9. Two distinct associations occur: (1) At McCarthy Point, 1–10 mm thick tourmaline-kornerupine-grandidierite layers are hosted within quartzofeldspathic gneiss; and (2) Seal Cove, where coexisting kornerupine and grandidierite occur within coarse-grained, metamorphic segregations with Mg-rich cores of cordierite-garnet-spinel-biotite-ilmenite and variably developed plagioclase halos. The segregations are hosted within biotite-bearing, plagio-feldspathic gneiss. Textural relationships from these localities indicate the stability of co-existing kornerupine and grandidierite.The grandidierite- and kornerupine-bearing segregations from Seal Cove largely postdate structures developed during a crustal thickening event (D2) which was coeval with peak metamorphism. At McCarthy Point, grandidierite, kornerupine and late-tourmaline growth predates, or is synchronous, with F3 fold structures developed during a extensive granulite grade, normal shearing event (D3) which occurred prior to, and synchronous with, near-isothermal decompression. Average pressure calculations on assemblages that coexist with the borosilicates at Seal Cove, indicate the prevailing conditions were 5.2–5.5 kbar at ∼ 750°C for formation of the grandidierite-kornerupine assemblage.

scholarly journals Trace Elements in Apatite as Genetic Indicators of the Evate Apatite-Magnetite Deposit, NE Mozambique

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1125
Author(s):  
Marek Slobodník ◽  
Veronika Dillingerová ◽  
Michaela Blažeková ◽  
Monika Huraiová ◽  
Vratislav Hurai
Keyword(s):  
Trace Elements ◽  
Inductively Coupled Plasma ◽  
Granulite Facies ◽  
Metasomatic Alteration ◽  
Partial Removal ◽  
Granulite Facies Metamorphism ◽  
Inductively Coupled ◽  
Mineral Assemblages ◽  
Granulite Complex ◽  
History Of

The Evate deposit is a Neoproterozoic (~590 Ma) magnetite-apatite-carbonate body emplaced parallel to foliation of the Monapo granulite complex in NE Mozambique. A complicated history of the deposit is recorded in apatite textures visualized in cathodoluminescence (CL) images. In spite of different solid and fluid inclusions, mineral assemblages, and the CL textures, electron probe microanalyses indicate relatively consistent apatite compositions corresponding to fluorapatite (XF = 0.51–0.73, XOH = 0.21–0.47, XCl = 0.02–0.06) with limited belovite- and cesanite-type substitutions. Laser ablation inductively coupled plasma mass spectrometric analyses show that apatites from unaltered magnetite-forsterite-spinel ores are depleted in Y, REE, Ba, and Sr compared to apatites from carbonate-anhydrite ores. Hydrothermally overprinted apatites with complex patchy domain CL textures are enriched in Y-REE in greenish-grey zones, Fe-U-Th in blue zones, and Mn-Sr-Ba in brown domains. Observed CL-emissions in the Evate apatites result from very subtle variations in REE, Mn, and U contents controlled by the variability of redox conditions. The decreased Th:U ratio in the hydrothermally overprinted apatites reflects the oxidation and partial removal of U4+ from the apatite structure during the interaction with oxidizing aqueous fluids capable of transporting U6+. Flat, LREE (La-Sm)-enriched chondrite-normalized patterns with Eu/Eu* = 0.7–1.4 and Ce/Ce* = 0.9–1.5, together with concentrations of diagnostic trace elements (Sr, Mn, Y, REE) are consistent with apatites from magmatic carbonatites and phoscorites. This study corroborates that the Evate deposit is a post-collisional orogenic carbonatite genetically linked with mafic plutonic rocks intruding the Monapo granulite complex after granulite-facies metamorphism, and later overprinted by intensive hydrothermalism. The Evate apatite is peculiar in retaining its pristine magmatic signature despite the extensive hydrothermal-metasomatic alteration accompanied by dissolution-reprecipitation.

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